Support Google Sheets API

[Torgen]

Add a command line option where the output file name will be interpreted as the ID of a google sheet, and a tab will be added to that sheet containing the grid.

[dgulotta]

I am not particularly motivated to add this, but a pull request would be welcome.

[Torgen]

I will see if I have time over the holiday break.
I assume you will want lazy dependencies? i.e. if you don't have the google APIs package installed, the web interface won't give you a place to enter the ID of the sheet to edit and the command line won't let you set that flag, but the other modes will still work?